Dextran

Abstract

A highly sensitive chemiluminescent ELISA for 2,4-dichlorophenoxyacetic acid (2,4-D), based on disposable thin-glass capillaries, was developed. The amino-silanised glass capillaries were coated by covalently attaching activated carboxymethyl (CM) dextran of different sizes, to which monoclonal antibodies were coupled. A competitive immunoassay was performed using horseradish peroxidase (HRP)-labelled 2,4-D and a commercially available chemiluminescent substrate. The bound fraction of the 2,4-D-HRP conjugate was quantified by measuring the intensity of the emitted light using a photomultiplier tube detector (PMT). The proposed method resulted in highly improved sensitivity with an IC₅₀ value of 0.002 ng ml⁻¹ for capillaries coated with high molecular weight dextran.